Generally, a silicon substrate with integrated circuits formed thereon is divided after an electrical operating test in a wafer state, with the semiconductor chips of an acceptable product being sealed in a package of plastic, ceramic or the like as an electric element. As the necessity arises, suitable connecting means such as BGA or the like is provided on the package so that the inner electric element and an outer circuit can be electrically interconnected. After sealing the package, an appropriate electrical test, such as a burn-in test is carried out and the acceptable semiconductor devices are shipped for sale. In connection with an electrical test such as the burn-in test, a socket in which the semiconductor device can be easily inserted or removed is used in view of the necessity of quickly testing a large number of semiconductor devices.
FIGS. 13(a)-13(d) show a socket made according to the prior art which is used for burn-in tests for semiconductor devices of the BGA type. Socket 201 has a base 211 and a cover 216. A plurality of test pins 243 are mounted on the bottom of base 211. The leg portion 244 of each test pin 243 protrudes downwardly from base 211 and the top part 241 is arranged in a selected array on base 211. A semiconductor device 208 of the BGA type is inserted into an accommodating part 231 provided at a prescribed location on base 211 and the semiconductor balls 209, arranged in the selected array on the bottom, are caused to engage the top part 241 of respective test pins 243. In this state, cover 216 is pivoted with a spring 222, provided between cover 216 and base 211, being compressed. Another spring 223 which cooperates with latch 217 mounted on cover 216 is compressed when cover 216 is forced downwardly covering base 211 with latch 217 being engaged with an engaging part 215 formed on base 211. The force of spring 223 maintains the cover in the closed position. With the cover closed and latched, semiconductor device 208 is compressed by the spring force of test pins 243 through cover 216 so that the electrically conductive balls 209 are pressed against the top part 241 of the test pins.
Leg parts 244 of test pins 243 are soldered to the wiring pattern (not shown) on the circuit board and, in the state where the electrically conductive balls 208 are pressed against top portions 241 of test pins 243, the electric element in semiconductor device 208 is interconnected with the circuit board or a test circuit that has been provided elsewhere through electrically conductive balls 209 and test pins 243. When the circuit is activated and a prescribed electrical signal is impressed on semiconductor device 208, the desired electrical test, e.g., a burn-in test, can be conducted in a desired atmosphere. After completion of the test, the engagement of latch 217 is released, cover 216 is opened, the semiconductor device 208 whose test has been completed is removed from base 211 and an untested semiconductor device 208 is inserted into accommodating part 231, thereby making it possible to speedily exchange semiconductor devices 208.
In the case of the above-described socket 201, however, it is necessary to exert a large force on semiconductor device 208 and press the lower portion of electroconductive balls 209 against the surface of top parts 241 of test pins 243 in order to obtain a suitable electrical connection between electrically conductive balls 209 and test pins 243. This has caused a problem in that the lower part of the electrically conductive balls 209 can become deformed and cause a degree of flatness and concomitant deterioration in the electrical connection between electrically conductive balls 209 that have been arranged in the selected array and test pins 243, thereby generating a failure in connection at the time of the actual mounting for its intended purpose. In recent years, moreover, the number of terminals of the semiconductor device 208 has been increased and the size of the distance between the electrically conductive balls 209 has been reduced. In order to cope with this trend, if the test pins were to be made finer, the spring force of the test pins 243 would be weakened with a resultant problem that the contact resistance between electrically conductive balls 209 and test pins 243 would increase. Further, in order to modify the upper portions 241 of test pins 243 to accommodate the reduced pitch of the electrically conductive balls 209, it would be necessary to reduce the pitch between the top parts 241 as well. This presents a problem in that the thickness of the partitions which provide electrical insulation would be excessively reduced so that the electrical isolation between the pins would be compromised.